Connection between entropy and total pressure

In summary, the conversation discusses the relationship between entropy, pressure, and friction. The speaker suggests that shear stress is a key factor in the entropy production term and the source term of the kinetic and internal energy transport equations. They also question if there is a direct connection between friction, total pressure, and entropy. They ask for clarification on the equation(s) for the rate of entropy generation per unit volume.
  • #1
obad
12
0
Hi guys,

I'm struggling to understand why an increase of entropy is directly linked with a decrease of total (stagnation) pressure. I have an idea, but I'm not sure if this is right.

My understanding of the problem is as follows:
Shear stress (friction) is a part of the entropy production term of the entropy transport equation. So when looking at this transport equation the role of friction is clear to me.
Furthermore shear stress is also contained in the source term of the kinetic energy and internal energy transport equation. Where friction converts kinetic energy into internal energy.
Now when looking at Bernoulli's equation, total pressure is a combination of the static and the dynamic pressure. Dynamic pressure is related to kinetic energy.

So could I say that friction simply reduces total pressure and increases entropy at the same time and there is actually no equation that describes a direct connection between these properties?

Cheers!
 
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  • #2
From your understanding, what is the equation (or equations) for the rate of entropy generation per unit volume?
 

1. What is entropy and how is it related to total pressure?

Entropy is a measure of the disorder or randomness in a system. It is related to total pressure through the Second Law of Thermodynamics, which states that the total entropy of a closed system will always increase over time. This means that as the total pressure in a system increases, so does the entropy.

2. How does an increase in total pressure affect entropy?

An increase in total pressure causes an increase in entropy because it results in a more disordered and chaotic system. This is because an increase in pressure leads to more collisions between particles, which creates more chaos and disorder.

3. Is there a mathematical relationship between entropy and total pressure?

Yes, there is a mathematical relationship between entropy and total pressure. This relationship is described by the equation ΔS = ΔQ/T, where ΔS is the change in entropy, ΔQ is the heat added to the system, and T is the temperature. This equation shows that an increase in total pressure will result in a larger change in entropy.

4. Can a decrease in total pressure lead to a decrease in entropy?

Yes, a decrease in total pressure can lead to a decrease in entropy. This is because a decrease in pressure causes the particles in the system to have less energy and move more slowly, resulting in a decrease in disorder and entropy.

5. How does the connection between entropy and total pressure relate to the properties of gases?

The connection between entropy and total pressure is related to the properties of gases through the ideal gas law, which states that pressure and temperature are directly proportional to each other. This means that as the temperature (and total pressure) of a gas increases, so does its entropy. Additionally, the movement and collisions of gas particles contribute to the overall entropy of a system.

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